BACKGROUND OF THE INVENTION
Technical Field
[0001] The present invention is used for a terminal for connectors that is crimped to a
terminal end of an electric wire made of an aluminum wire material; and relates to
a terminal material plated with tin or tin alloy on a surface of a substrate made
of copper or copper alloy, a terminal made of the terminal material and an electric
wire termination structure using the terminal.
Background Art
[0003] Conventionally, a terminal end of an electric wire formed from copper or copper alloy
is crimped with a terminal formed from copper or copper alloy; and the terminal is
connected to a terminal of another equipment, so that the electric wire is connected
to that equipment. In order to reduce a weight of the electric wires and so forth,
there is a case in which the electric wires are formed from aluminum or aluminum alloy
instead of copper or copper alloy.
[0004] For example, Patent Document 1 discloses an electric wire with terminals in which
a terminal made of copper or copper alloy with tin plating is crimped to an electric
wire made of aluminum or aluminum alloy, as an electric wire with terminals installed
on vehicles such as automobiles.
[0005] Forming the electric wire (a conducting wire) from aluminum or aluminum alloy and
forming the terminal from copper or copper alloy, there is a case in which electrical
corrosion may be occurred owing to a potential difference between different metals
if water moves into a crimp part between the terminal and the electric wire. Furthermore,
there is a case in which an electrical resistivity be increased or a crimping forth
be decreased in the crimp part with the corrosion of the electric wire.
[0006] For preventing this corrosion, in Patent Document 1 for example, an anti-corrosion
layer made of metal (zinc or zinc alloy) having sacrificial anti-corrosion property
to a substrate layer is formed between the substrate layer and a tin layer.
[0007] An electrical contact material for connectors shown in Patent Document 2 has a substrate
made of a metal material, an alloy layer formed on the substrate, and a conductive
film layer formed on a surface of the alloy layer. The alloy layer essentially contains
Sn (tin), and includes one or more additive elements M selected from Cu, Zn, Co, Ni
and Pd. The conductive film layer including hydroxide oxide Sn
3O
2(OH)
2 and the like are known.
[0008] An Sn plating material disclosed in Patent Document 3 is known as an example of adding
Zn to Sn. The Sn plating Material has an undercoat Ni plating layer, an intermediate
Sn-Cu plating layer and a surface Sn plating layer on a surface of a copper or a copper
alloy in this order: the undercoat Ni plating layer is formed from Ni or Ni alloy:
the intermediate Sn-Cu plating layer is formed from an Sn-Cu type alloy in which at
least an Sn-Cu-Zn alloy layer is formed at a side being in contact with the surface
Sn plating layer: the surface Sn plating layer is formed from an Sn alloy including
Zn 5 to 1000 ppm by mass: and a highly-concentrated Zn layer with a Zn concentration
more than 0.2% by mass to 10% by mass on an outermost surface is further included.
Citation List
Patent Documents
[0009]
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No.
2013-218866
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No.
2015-133306
[Patent Document 3] Japanese Unexamined Patent Application, First Publication No.
2008-285729
SUMMARY OF INVENTION
Technical Problem
[0010] However, if the anti-corrosion layer formed from zinc or zinc alloy is provided as
the undercoat as in Patent Document 1, there is a problem in which adhesion property
between the anti-corrosion layer and the Sn plating is deteriorated because Sn substitution
is occurred by performing Sn plating on the anti-corrosion layer.
[0011] Even in a case in which a hydroxide oxide layer of Sn
3O
2(OH)
2 is provided as in Patent Document 2, there is a problem in which durability is low
since the hydroxide oxide layer defects immediately when being exposed in a corrosion
environment or heating environment. If an Sn-Zn alloy layer is layered on an Sn-Cu
type alloy layer and a zinc highly-concentrated layer is provided on an outermost
layer as in Patent Document 3, there is a problem of productivity of Sn-Zn alloy plating
being low, and also anti-corrosion effect of an aluminum wire material cannot be obtained
in a case in which copper of the Sn-Cu alloy layer is exposed on an surface layer.
[0012] As a contact material used for connectors, contact resistance is required to be reduced,
and it is necessary to reduce an increase of contact resistance particularly when
sliding wear is occurred.
[0013] The present invention is achieved in consideration of the above circumstances, and
has an object to provide a terminal material for connectors, a terminal made of the
terminal material, and an electric wire termination structure using the terminal,
in which a substrate formed from copper or copper alloy is used for the terminal crimped
to the terminal end of the electric wire formed from an aluminum wire material so
electrical corrosion can be efficiently reduced and also contact resistance is low.
Solution to Problem
[0014] A terminal material for connectors according to the present invention includes a
substrate made of copper or copper alloy, and a zinc layer made of zinc alloy and
a tin layer made of tin alloy layered on the substrate in this order: in the zinc
layer and the tin layer, an adhesion amount of tin contained in a whole is not less
than 0.5 mg/cm
2 and not more than 7.0 mg/cm
2, an adhesion amount of zinc contained in the whole is not less than 0.07 mg/cm
2 and not more than 2.0 mg/cm
2, and a zinc content percentage in a vicinity of a surface is not less than 0.2% by
mass and not more than 10.0% by mass.
[0015] In this terminal material for connectors, under the tin layer at the surface layer,
the zinc layer having a corrosion potential nearer to that of aluminum than that of
tin is formed, and zinc is contained in a vicinity of a surface: so that an effect
of preventing corrosion of an aluminum wire is high.
[0016] In this case, if the adhesion amount of tin contained in the whole zinc layer and
tin layer is less than 0.5 mg/cm
2, some of zinc is exposed while working, and the contact resistance is increased.
If the adhesion amount of tin exceeds 7.0 mg/cm
2, zinc is not sufficiently diffused to the surface, so that the corrosion current
value is increased. An appropriate range of the adhesion amount of tin is 0.7 mg/cm
2 to 2.0 mg/cm
2 (inclusive).
[0017] If the adhesion amount of zinc is less than 0.07 mg/cm
2, zinc is not sufficiently diffused to the surface of the tin layer, and the corrosion
current value is increased. If the adhesion amount of zinc exceeds 2.0 mg/cm
2, zinc is excessively diffused and the contact resistance is increased. An appropriate
range of the adhesion amount of zinc is 0.2 mg/cm
2 to 1.0 mg/cm
2 (inclusive).
[0018] If the zinc content percentage in the vicinity of the surface exceeds 10.0% by mass,
a large amount of zinc is exposed from the surface and the contact resistance is deteriorated.
If the zinc content percentage is less than 0.2% by mass in the vicinity of the surface,
anti-corrosion effect is not sufficient. The zinc content percentage is preferably
0.4% by mass to 5.0% by mass (inclusive).
[0019] As a desired embodiment of the terminal material for connectors of the present invention,
it is preferable that a corrosion potential to a silver-silver chloride be not more
than -500 mV and not less than -900 mV.
[0020] It is possible to reduce the corrosion current low and have an excellent anti corrosion
effect.
[0021] As an appropriate embodiment of the terminal material for connectors of the present
invention, it is preferable that at least one of the tin layer and the zinc layer
contains one or more of nickel, iron, manganese, molybdenum, cobalt, cadmium and lead
as an additive element and an adhesion amount thereof is not less than 0.01 mg/cm
2 and not more than 0.3 mg/cm
2.
[0022] Containing these additives, zinc is prevented from excessive diffusion, and there
is an effect of reducing generation of whiskers. If the adhesion amount thereof is
less than 0.01 mg/cm
2, zinc is excessively diffused to the surface of tin, so that the contact resistance
is increased and the effect of reducing the whiskers is decreased. If the adhesion
amount exceeds 0.3 mg/cm
2, zinc is not sufficiently diffused, and the corrosion current is increased.
[0023] As an appropriate embodiment of the terminal material for connectors of the present
invention, it is preferable that the adhesion amount of the zinc be not less than
one times and not more than 10 times of the adhesion amount of the additive element.
[0024] These adhesion amounts have relations in this range, so that the generation of the
whiskers is further prevented.
[0025] As an appropriate embodiment of the terminal material for connectors of the present
invention, it is preferable that a ground layer made of nickel or nickel alloy be
formed between the substrate and the zinc layer; and the ground layer have a thickness
not less than 0.1 µm and not more than 5 µm and a nickel content percentage not less
than 80% by mass.
[0026] The ground layer between the substrate and the zinc layer has functions of improving
adhesion between them and preventing diffusion of copper to the zinc layer and the
tin layer from the substrate made of copper or copper alloy. If the thickness of the
ground layer is less than 0.1 µm, the effect of preventing copper from diffusion is
poor; if it exceeds 5.0 µm, breakages may be easily occurred while the press working.
If the nickel content percentage is less than 80% by mass, the effect of preventing
diffusion of copper to the zinc layer and the tin layer is poor.
[0027] As an appropriate embodiment of the terminal material for connectors of the present
invention, it is formed to be a belt sheet shape, and in a carrier part along a length
direction thereof, terminal members formed to be terminals by a press working are
coupled to the carrier part with intervals along a length direction of the carrier
part.
[0028] A terminal of the present invention is a terminal formed from the above mentioned
terminal material for connectors: and in an electric wire termination structure of
the present invention the terminal is crimped to an end of an electric wire made of
aluminum or aluminum alloy.
[0029] There is a case in which the zinc layer and the tin layer cannot clearly recognized
because of mutual diffusion. The terminal material for connectors in this case includes
a substrate made of copper or copper alloy, and a tin zinc layer containing zinc and
tin layered on the substrate; in the tin zinc layer, an adhesion amount of tin contained
in a whole thereof is not less than 0.5 mg/cm
2 and not more than 7.0 mg/cm
2, an adhesion amount of zinc is not less than 0.07 mg/cm
2 and not more than 2.0 mg/cm
2, and a zinc content percentage is not less than 0.2% by mass and not more than 10%
by mass in a vicinity of a surface.
Advantageous Effects of Invention
[0030] According to the terminal material for connectors of the present invention, because
the zinc layer and the tin layer is formed on the substrate and zinc is contained
in the vicinity of the surface, the anti-corrosion effect against the electric wire
made of aluminum is improved: because the zinc layer is formed between the tin layer
and the substrate, it is possible to prevent an increase of the electrical resistivity
and deterioration of the adhesion by preventing the electrical corrosion with the
aluminum-made electric wire even when the tin layer is disappeared. Furthermore, it
is possible to reduce also the rise of the contact resistance when it is worn by sliding.
BRIEF DESCRIPTION OF DRAWINGS
[0031]
[FIG. 1] It is a sectional view schematically showing an embodiment of a terminal
material for connectors of the present invention.
[FIG. 2] It is a plan view of the terminal material of the embodiment.
[FIG. 3] It is a perspective view showing an example of a terminal on which the terminal
material of the embodiment is applied.
[FIG. 4] It is a frontal view showing a terminal end of an electric wire to which
the terminal of FIG. 3 is crimped.
DESCRIPTION OF EMBODIMENTS
[0032] A terminal material for connectors, a terminal, and an electric wire termination
structure of an embodiment according to the present invention will be explained.
[0033] A terminal material for connectors 1 of the present embodiment is a strip material
formed to be a belt sheet shape for forming terminals as a whole thereof is shown
in FIG. 2: on a carrier part 21 along a longitudinal direction, terminal members 22
formed to be terminals are arranged in a longitudinal direction of the carrier part
21 with intervals: and the respective terminal members 22 are coupled to the carrier
part 21 with narrow width coupling parts 23 therebetween. The terminal members 22
are formed to have a shape of a terminal 10 shown in FIG. 3 for example, and finished
as the terminals 10 by being cut off from the coupling parts 23.
[0034] The terminal 10 is shown as a female terminal in an example of FIG. 3, having a connecting
part 11 to which a male terminal (not illustrated) is fit inserted, a core wire crimp
part 13 to which an exposed core wire 12a of an electric wire 12 is crimped, and a
cover crimp part 14 to which a cover part 12b of the electric wire 12 is crimped are
integrally formed in this order from a tip end.
[0035] FIG. 4 shows a termination structure in which the terminal 10 is crimped to the electric
wire 12: the core wire crimp part 13 is directly in contact with the core wire 12a
of the electric wire 12.
[0036] In this terminal material for connectors 1, as schematically showing a section thereof
in FIG. 1, an ground layer 3 formed of nickel or nickel alloy, a zinc layer 4 formed
of zinc alloy, and a tin layer 5 formed of tin alloy are layered on a substrate 2
in this order.
[0037] A composition of the substrate 2 is not particularly limited but formed from copper
or a copper alloy.
[0038] The ground layer 3 has a thickness 0.1 µm to 5.0 µm (inclusive) and a nickel content
percentage 80% by mass or more. The ground layer 3 improve adhesion between the substrate
2 and the zinc layer 4 and prevent diffusion of copper from the substrate 2 to the
zinc layer 4 and the tin layer 5: if the thickness thereof is less than 0.1 µm, an
effect of preventing the diffusion of copper is poor; if it exceeds 5.0 µm, breakages
are easy to be occurred while a pressing work. It is more preferable that the thickness
of the ground layer 3 be 0.3 µm to 2.0 µm (inclusive).
[0039] If the nickel content percentage is less than 80% by mass, the effect of preventing
diffusion of the copper to the zinc layer 4 and the tin layer 5 is poor. The nickel
content is preferably 90% by mass or more.
[0040] Tin and zinc are diffused into the zinc layer 4 and the tin layer 5 mutually: an
adhesion amount of the tin is 0.5 mg/cm
2 to 7.0 mg/cm
2 (inclusive) and an adhesion amount of the zinc is 0.07 mg/cm
2 to 2.0 mg/cm
2 (inclusive), which are contained in the whole (the whole between an interface to
the ground layer 3 and the outermost surface).
[0041] When the adhesion amount of the tin is less than 0.5 mg/cm
2, some of zinc is exposed while working, so that the contact resistance is increased.
When the adhesion amount of tin exceeds 7.0 mg/cm
2, zinc is not sufficiently diffused to the surface, so that a corrosion current value
is increased. An appropriate range of the adhesion amount of tin is 0.7 mg/cm
2 to 2.0 mg/cm
2 (inclusive).
[0042] When the adhesion amount of zinc is less than 0.07 mg/cm
2, zinc is not sufficiently diffused to the surface of the tin layer 5, so that the
corrosion current value is increased. When the adhesion amount of zinc exceeds 2.0
mg/cm
2, zinc is excessively diffused, so that the contact resistance is increased. An appropriate
range of the adhesion amount of zinc is 0.2 mg/cm
2 to 1.0 mg/cm
2 (inclusive).
[0043] The adhesion amount means a content per a unit area (mg/cm
2) in the whole of the zinc layer 4 and the tin layer 5.
[0044] In this case, a zinc content percentage in the vicinity of a surface is 0.2% by mass
to 10.0% by mass (inclusive). When it exceeds 10.0% by mass, a large amount of zinc
is exposed from the surface, so that the contact resistance is deteriorated. When
the zinc content percentage in the vicinity of the surface is less than 0.2% by mass,
the anti-corrosion effect is not sufficient. The zinc content percentage is preferably
0.4% by mass to 5.0% by mass (inclusive). In this case, the vicinity of the surface
means a range of a depth 0.3 µm from the surface of the whole film.
[0045] It is preferable that a thickness of the zinc layer 4 be 0.1 µm to 2.0 µm (inclusive),
and a thickness of the tin layer 5 be 0.2 µm to 5.0 µm (inclusive). Since the zinc
layer 4 and the tin layer 5 are mutually diffused, there is a case in which an interface
between the zinc layer 4 and the tin layer 5 is difficult to be recognized: moreover,
there is a case in which the zinc layer 4 and the tin layer 5 cannot be clearly recognized
but can be a film recognized as a tin zinc layer containing zinc and tin, in accordance
with the respective thicknesses and an extent of mutual diffusion.
[0046] At least one of the tin layer 5 and the zinc layer 4 contains one or more of nickel,
iron, manganese, molybdenum, cobalt, cadmium, and lead as an additive element: an
adhesion amount thereof is preferably 0.01 mg/cm
2 to 0.3 mg/cm
2 (inclusive). As below-mentioned, the zinc layer 4 contains these additive elements
in the embodiment. In a case in which it is the tin zinc layer, it is enough that
the whole thereof contains the above-mentioned additive element.
[0047] Containing these additives, it is effective for restrain the excessive diffusion
of zinc and generation of whiskers. When the adhesion amount thereof is less than
0.01 mg/cm
2, zinc is excessively diffused to the surface of tin, so that the contact resistance
is increased and the effect of restraining the whisker is poor. If the adhesion amount
exceeds 0.3 mg/cm
2, zinc is not sufficiently diffused and the corrosion current is increased.
[0048] The above mentioned adhesion amount of zinc is desirable in a range not less than
1 times and not more than 10 times of the adhesion amount of these additive elements.
By a relation in this range, the whiskers are more prevented from generating.
[0049] The terminal material for connecters 1 having the above structure has an excellent
anti-corrosion effect, since the corrosion potential to a silver-silver chloride electrode
is not more than -500 mV and not less than -900 mV (-500 mV to -900 mV) and a corrosion
potential of aluminum is not more than 700 mV and not less than -900 mV.
[0050] Subsequently, a manufacturing method of the terminal material for connectors 1 will
be explained.
[0051] A sheet material made of copper or copper alloy is prepared as the substrate 2. Performing
a cutting work, a punching work and the like on this sheet material, a strip material
in which terminal members 22 are coupled with the carrier part 21 with the coupling
parts 23 therebetween as shown in FIG. 2 is formed. Then, after cleaning surfaces
of this strip material by performing treatments of a degreasing, a pickling and the
like, a nickel or nickel plating treatment for forming the ground layer 3, a zinc
or zinc alloy plating treatment for forming the zinc layer 4, and a tin or tin alloy
plating treatment for forming the tin layer 5 are performed in this order.
[0052] The nickel or nickel alloy plating for forming the ground layer 3 is not limited
if a dense film with mainly containing nickel can be obtained: it can be formed by
electroplating using a known Watts bath, a sulfamic acid bath, a citric acid bath
or the like. For nickel alloy plating, a nickel tungsten (Ni-W) alloy, a nickel phosphorous
(N-P) alloy, a nickel cobalt (Ni-Co) alloy, a nickel chromium (Ni-Cr) alloy, a nickel
iron (Ni-Fe) alloy, a nickel zinc (Ni-Zn) alloy, a nickel boron (Ni-B) alloy and the
like can be used.
[0053] Considering the terminal 10 in a press bending property and a barrier property against
copper, a pure nickel plating obtained by the sulfamic acid bath is appropriate.
[0054] The zinc or zinc alloy plating for forming the zinc layer 4 is not specifically limited
if a dense film can be obtained with a prescribed composition: a known sulfate bath,
a chloride bath, a zincate bath or the like can be used for the zinc plating. For
zinc alloy plating, the sulfate bath, the chloride bath, an alkaline bath can be used
for zinc-nickel alloy plating; or a complexing agent bath containing a citric acid
and the like can be used for tin-zinc alloy plating. A film of zinc cobalt alloy plating
can be formed using the sulfate bath: a film of zinc-manganese alloy plating can be
formed using a sulfate bath containing citric acid: and a film of zinc-molybdenum
plating can be formed using the sulfate bath.
[0055] Tin or tin alloy plating for forming the tin layer 5 can be performed by known methods:
i.e., electroplating can be performed using an organic acid bath (i.e., a phenol sulfonic
acid bath, an alkane sulfonic acid bath, or an alkanol sulfonic acid bath), an acidic
bath such as a fluoboric acid bath, a halogen bath, a sulfuric acid bath, a pyrophosphoric
acid bath and the like, or an alkaline bath such as a potassium bath, a sodium bath
or the like.
[0056] As explained above, the nickel or nickel alloy plating, the zinc plating or the zinc
alloy plating, and the tin or tin alloy plating are performed in this order on the
substrate 2, and then the heat treatment is performed.
[0057] In this heat treatment, it is heated so that a surface temperature of an object is
30°C to 190°C (inclusive). By this heat treatment, zinc in a zinc plating or zinc
alloy plating layer is diffused into a tin plating layer. As zinc is rapidly diffused,
it is enough to be exposed at temperature 30°C or higher for 24 hours or longer. However,
it is not heated to temperature higher than 190°C, because zinc alloy repels melted
tin and forms parts where tin is repelled on the tin layer 5.
[0058] In the terminal material for connectors 1 manufactured as above, as a whole, the
ground layer 3 formed of nickel or nickel alloy, the zinc layer 4 formed of zinc or
zinc alloy, and the tin layer 5 are laminated on the substrate 2 in this order. Alternatively,
as described above, the tin zinc layer in which the zinc layer 4 and the tin layer
5 are integrated is formed.
[0059] Then, the shape of the terminal 10 shown in FIG. 3 is formed by a pressing work and
the like as it remains the strip material: and cutting the coupling parts 23, the
terminals 10 are formed.
[0060] FIG. 4 shows a termination structure in which the electric wire 12 is crimped on
the terminal 10: the core wire crimp part 13 is in directly contact with the core
wire 12a of the electric wire 12.
[0061] This terminal 10 is effective to prevent the corrosion of the aluminum wire and can
effectively prevent electric erosion, even in a state in which it is crimped to the
aluminum core wire 12a; because the tin layer 5 contains zinc having nearer corrosion
potential to aluminum than that of tin.
[0062] Since the plating treatment and the heat treatment were performed in the state of
the strip material of FIG. 2, the substrate 2 is not exposed even at end surfaces
of the terminal 10, so it is possible to show an excellent anti-corrosion effect.
[0063] Moreover, the zinc layer 4 is formed under the tin layer 5: even if all or a part
of the tin layer 5 is lost by abrasion and the like at the worst, since the zinc layer
4 thereunder has the nearer corrosion potential to that of aluminum, it is possible
to reliably prevent the electric erosion. Also when it is the integrated film as the
tin zinc layer, the electric erosion can be prevented since zinc is contained in the
vicinity of the surface: and since the zinc content is high in the vicinity of the
interface to the ground layer 3, even if sliding wear and the like is occurred, it
is effectively prevented by the zinc in the high concentration part to occur the electric
erosion.
[0064] Furthermore, it is possible to prevent also the contact resistance from rising owing
to the sliding wear as a connector.
[0065] The present invention is not limited to the above-described embodiment(s) and various
modifications may be made without departing from the scope of the present invention.
---EXAMPLES---
[0066] Using a copper sheet of C1020 (oxygen free copper) of JIS standard as the substrate,
degreasing and pickling it, and then nickel plating, zinc plating or zinc alloy plating
and tin plating as the ground layer were performed in this order. Principal conditions
of plating are as follows: the zinc content percentage in the zinc layer was controlled
by varying a proportion of zinc ion and additive alloy element ion in the plating
solution. Plating condition of zinc nickel alloy mentioned below is an example in
which the zinc content is 15% by mass. In Sample 17, zinc or zinc alloy plating was
not performed, the copper sheet was degreased and pickled, and nickel plating and
tin plating were performed sequentially. In Samples 1 to 12, 17 and 19, nickel plating
as the ground layer was not performed. As a sample in which the nickel alloy plating
was performed on the ground layer, in Sample 14 nickel-phosphorus plating was performed.
In Sample 3 to 16, elements described in Table 1 were added when the zinc alloy plating
was performed.
--Condition of Nickel Plating--
[0067]
Composition of Plating Bath
Nickel Sulfamate: |
300 g/L |
Nickel Chloride: |
5 g/L |
Boric Acid: |
30 g/L |
Bath Temperature: 45°C
Current Density: 5 A/dm
2
--Condition of Zinc Plating--
[0068] Zinc Sulfate Heptahydrate: 250 g/L
Sodium Sulfate: 150 g/L
pH = 1.2
Bath Temperature: 45°C
Current Density: 5 A/dm
2
--Condition of Nickel Zinc Alloy Plating--
Composition of Plating Bath
[0069] Zinc Sulfate Heptahydrate: 75 g/L
Nickel Sulfate Hexahydrate: 180 g/L
Sodium Sulfate: 140 g/L
pH = 2.0
Bath Temperature: 45°C
Current Density: 5 A/dm
2
--Condition of Tin Zinc Alloy Plating--
Composition of Plating Bath
[0070] Tin (II) Sulfate: 40 g/L
Zinc Sulfate Heptahydrate: 5 g/L
Trisodium Citrate: 65 g/L
Nonionic Surfactant: 1 g/L
pH = 5.0
Bath Temperature: 25°C
Current Density: 3 A/dm
2
--Condition of Zinc Manganese Alloy Plating--
Composition of Plating Bath
[0071] Manganese Sulfate Monohydrate: 110 g/L
Zinc Sulfate Heptahydrate: 50 g/L
Trisodium Citrate: 250 g/L
pH = 5.3
Bath Temperature: 30°C
Current Density: 5 A/dm
2
--Condition of Tin Plating--
[0072] Composition of Plating Bath
Methanesulfonic Acid Tin: 200 g/L
Methanesulfonic Acid: 100 g/L
Bath Temperature: 35°C
Current Density: 5 A/dm
2
[0073] On the plated copper sheets, the heat treatment was performed at temperature 30°C
to 190°C for in a range of 1 hour to 36 hours to make the samples.
[0074] With respect to the obtained samples, respectively measured were the thickness of
the ground layer, the nickel content in the ground layer, the adhesion amounts of
tin in the zinc layer and the tin layer, the adhesion amount of zinc in the zinc layer
and the tin layer, the zinc content percentage in the zinc layer and the tin layer
in the vicinity of the surface, and the adhesion amount of the additive elements other
than tin and zinc in the zinc layer and the tin layer.
[0075] The thickness of the ground layer was measured by observing a section with a scanning
ion microscope.
[0076] The nickel content percentage in the ground layer was measured as follows: forming
observation samples by thinning samples to 100 nm or less with a focused ion beam
device FIB (model No. SMI3050TB) made by Seiko Instrument Inc.; observing the observation
samples with a scanning transmission electron microscope STEM (model No. JEM-2010F)
made by JEOL Ltd. (formerly called Japan Electron Optics Laboratory Co., LTD) at an
acceleration voltage 200 kV; and measuring by an energy dispersive X-ray spectrometer
EDS (made by Thermo) belonging to the STEM.
[0077] The adhesion amounts of tin, the adhesion amount of zinc, and the adhesion amount
of the other additive elements were measured in the zinc layer and the tin layer as
follows. Masking the terminal material so that an area is known, it is soaked in a
prescribed amount of plating stripping solution (Stripper L-80) made by Leybold Co.,
Ltd. so as to melt the tin layer and the zinc layer. Diluting this solution with dilute
hydrochloric acid in a measuring flask to a prescribed amount; measuring density of
element in the solution with a frame atom light absorption photometer; and dividing
the density by the measuring area: and it was calculated. Using the above-mentioned
plating stripping solution, it is possible to measure the element amount contained
in the zinc layer and the tin layer without melting the substrate and the nickel plating
layer.
[0078] The content percentage of zinc in the vicinity of the surface was measured at the
surface of the samples using an electron probe micro analyzer EPMA (model No. JXA-8530F)
made by JEOL Ltd. at an acceleration voltage 6.5 V and a beam diameter 30 µm. Because
the acceleration voltage is low as 6.5 kV for this measurement, measured is the zinc
content percentage in a depth about 0.3 µm from the surface of the tin layer.
[0079] Regarding the corrosion potential: cutting the sample 10 mm × 50 mm, coating copper
exposed parts such as the end surfaces with epoxy resin, then soaking in a sodium
chloride solution 23°C and 5% by mass: and the corrosion potential was obtained as
an average value of measuring for 24 hours with 1 minute intervals using a function
of measuring a spontaneous-potential of HA1510 made by Hokuto Denko Corporation, with
a reference electrode that is a silver-silver chloride electrode (Ag/AgCl electrode)
for a double-junction system made by Metrohm AG, in which a saturated potassium chloride
solution is filled as an internal tube fluid.
[0080] The measurement results are shown in Table 1.
[Table 1]
Sample No. |
GROUND LAYER |
TIN LAYER AND ZINC LAYER |
Corrosion Potential (mV vs. Ag/AgCl) |
THICKNESS (µm) |
Ni Content Percentage (%) |
ADHESION AMOUNT |
Zinc Content Percentage in Vicinity of Surface (% by mass) |
Adhesion Amount of Additional Element (mg/cm2) |
TIN (mg/cm2) |
ZINC (mg/cm2) |
1 |
0 |
- |
0.5 |
2 |
10 |
- |
-940 |
2 |
0 |
- |
7 |
0.07 |
0.2 |
- |
-490 |
3 |
0 |
- |
6.5 |
0. 1 |
0.4 |
0.4 (Co) |
-510 |
4 |
0 |
- |
0.8 |
1.9 |
5 |
0. 007 (Pb) |
-890 |
5 |
0 |
- |
2 |
0.2 |
1.2 |
0.25 (Ni) |
-520 |
6 |
0 |
- |
2 |
0.2 |
0.9 |
0.3 (Fe) |
-540 |
7 |
0 |
- |
2 |
0.2 |
3. 1 |
0.015 (Mn) |
-750 |
8 |
0 |
- |
2 |
0.2 |
2. 1 |
0.01 (Mo) |
-730 |
9 |
0 |
- |
2 |
0.2 |
1.1 |
0.25 (Co) |
-590 |
10 |
0 |
- |
2 |
0. 2 |
1.8 |
0.3 (Cd) |
-550 |
11 |
0 |
- |
2 |
0.2 |
2.5 |
0.01 (Pb) |
-800 |
12 |
0 |
- |
2 |
0.2 |
1.1 |
0. 2 (Fe) |
-580 |
13 |
0.05 |
100 |
2 |
0.2 |
1.9 |
0.02 (Ni) |
-710 |
14 |
0.1 |
90 (Ni-P) |
1.5 |
0.5 |
1.3 |
0. 07 (Ni) |
-680 |
15 |
5 |
100 |
1.5 |
0.5 |
1.1 |
0.07 (Ni) |
-690 |
16 |
0.5 |
100 |
1.5 |
0.5 |
1.2 |
0. 07 (Ni) |
-670 |
17 |
0 |
- |
1. 5 |
0 |
0 |
- |
-420 |
18 |
5.6 |
70 (Ni-Fe) |
0.4 |
2.2 |
12 |
- |
-920 |
19 |
0 |
- |
8 |
0. 05 |
0.3 |
- |
-430 |
[0081] Regarding the obtained samples, measured and evaluated were the corrosion current,
the bending workability, generation status of the whiskers, and the contact resistance.
--Corrosion Current--
[0082] Regarding the corrosion current, arranging a pure aluminum wire coated with resin
other than an exposure part of a diameter 2 mm and a sample coated with resin other
than an exposure part of a diameter 6 mm so that the exposure parts thereof face to
each other with a distance 1 mm, the corrosion current was measured between the aluminum
wire and the sample in salt water of 23°C and 5% by mass. In order to measure the
corrosion current, a zero shunt ammeter HA1510 made by Hokuto Denko Corporation was
used: the corrosion currents between the sample after heating for 1 hour ate 150°C
and the sample before heating were compared. A mean current value for 1000 minutes
and a mean current value further longer test was performed on for 1000 to 3000 minutes
were compared.
--Bending Workability--
[0083] Regarding the bending workability, cutting a test piece to have a longitudinal direction
along a rolling direction, and using a W-shaped bending test tool regulated in JISH3110,
a bending work was performed with a load 9.8 × 10
3 N orthogonal to the rolling direction. Then, observation was performed with a stereoscopic
microscope. Evaluation of the bending workability: a level was evaluated as "excellent"
if a clear crack was not recognized in a bended part after the test; a level was evaluated
as "good" even though some cracks were recognized, if an exposure by the cracks of
a copper alloy base material was not recognized; and a level was evaluated as "bad"
if the copper alloy base material was exposed by the cracks.
--Generation Status of Whiskers--
[0084] Regarding evaluation of the generation status of the whiskers: leaving a flat sheet
sample cut into 1 cm
2 square for 1000 hours under condition of 55°C and 95% RH (relative humidity), and
observing 3 view fields by × 100 magnification with an electron microscope, a length
of a longest whisker in that was measured. It was evaluated as "excellent" if no generation
of whisker was recognized; it was evaluated as "good" even though the whiskers were
generated but if the length thereof is less than 50 µm; it was evaluated as "fair"
if the length of the whisker was not less than 50 µm and less than 100 µm; and it
was evaluated as "bad" if the length of the whisker was 100 µm or more.
--Contact Resistance--
[0085] The measurement method of the contact resistance was in accordance with JCBA-T323:
using a four-terminal contact-resistance test device (made by Yamasaki Seiki Research
Institute, Inc. CRS-113-AU), the contact resistance was measured at a load 0.98 N
on a sliding test (1 mm). The measurement was performed on a plating surface of the
flat sheet sample.
[0086] These results are shown in Table 2.
[Table 2]
Sample No. |
CORROSION CURRENT (µA) |
Bending Workability |
Whiskers |
Contact Resistance (mΩ) |
Before Heating |
After Heating |
1 |
4.1 |
6.1 |
GOOD |
FAIR |
2. 0 |
2 |
4.0 |
6.5 |
GOOD |
FAIR |
2.1 |
3 |
2.1 |
5.5 |
GOOD |
GOOD |
1.9 |
4 |
3.0 |
6.2 |
GOOD |
FAIR |
1.5 |
5 |
2.1 |
3.5 |
GOOD |
GOOD |
0.8 |
6 |
1.8 |
2.5 |
GOOD |
GOOD |
0.9 |
7 |
1.2 |
3.5 |
GOOD |
GOOD |
0.7 |
8 |
1.3 |
3.1 |
GOOD |
GOOD |
0.6 |
9 |
2.9 |
4.5 |
GOOD |
GOOD |
0.7 |
10 |
1.9 |
4.0 |
GOOD |
GOOD |
0.8 |
11 |
1.1 |
2.0 |
GOOD |
GOOD |
0.8 |
12 |
1.0 |
1.9 |
GOOD |
EXCELLENT |
0.9 |
13 |
1.1 |
1.8 |
EXCELLENT |
EXCELLENT |
0.8 |
14 |
0.9 |
1.1 |
EXCELLENT |
EXCELLENT |
0.5 |
15 |
0.8 |
0.9 |
EXCELLENT |
EXCELLENT |
0.5 |
16 |
0.8 |
1.2 |
EXCELLENT |
EXCELLENT |
0.5 |
17 |
8.5 |
8.5 |
GOOD |
BAD |
0.6 |
18 |
5.8 |
7.5 |
BAD |
BAD |
5.2 |
19 |
8.1 |
8.2 |
BAD |
BAD |
0.7 |
[0087] It can be recognized from the results shown in Table 2 that the corrosion current
was low, the bending workability was good, the whiskers were not generated, or the
length were short even if the whiskers were generated, and the contact resistance
was low in Samples 1 to 16: in Samples 1 to 16, in the zinc layer and the tin layer,
the adhesion amount of tin contained in the whole was 0.5 mg/cm
2 to 7.0 mg/cm
2 (inclusive), the adhesion amount of zinc was 0.07 mg/cm
2 to 2.0 mg/cm
2 (inclusive), and the zinc content percentage is 0.2% by mass to 10.0% by mass (inclusive)
in the vicinity of the surface. Above all, in Samples 3 and Samples 5 to 16 containing
one of additive elements of nickel, iron, manganese, molybdenum, cobalt, cadmium,
and lead with 0.01 mg/cm
2 to 0.3 mg/cm
2 (inclusive), the generation of the whiskers was especially prevented. Because Samples
14 to 16 had the ground layer formed with the thickness 0.1 µm to 5.0 µm (inclusive)
and the nickel content percentage 80% or more between the substrate and the zinc layer,
Samples 14 to 16 had more excellent effect of preventing the electrical corrosion
even after heating than Samples 1 to 15 without the ground layer.
[0088] Meanwhile, in Sample 17 of Comparative Example, the corrosion potential was high
and the corrosion current was high because there was no zinc layer (i.e., zinc was
not adhered). In Sample 18, the adhesion amount of tin was small, the adhesion amount
of zinc was large, and the nickel content percentage in the ground layer was low:
so that the corrosion current value was deteriorated and the bending workability was
inferior after heating: the contact resistance was deteriorated because the zinc diffusion
was excessive and the corrosion potential was not higher than -900 mV vs Ag/AgCl.
In Sample 19, because the adhesion amount of tin was large and the adhesion amount
of zinc was small, the corrosion current value was high, and cracks were generated
when the bending work was performed.
Industrial Applicability
[0089] This invention can be used as a terminal for connectors used for connecting electric
wires in automobiles, consumer products and the like; especially, it can be used for
a terminal crimped to a terminal end of electric wires made of aluminum wire material.
Reference Signs List
[0090]
- 1
- Terminal material for connectors
- 2
- Substrate
- 3
- Ground layer
- 4
- Zinc layer
- 5
- Tin layer
- 10
- Terminal
- 11
- Connecting part
- 12
- Electric wire
- 12a
- Core wire
- 12b
- Cover part
- 13
- Core wire crimp part
- 14
- Cover crimp part